The current world population is around 7 billion living people and 107 billion dead people. Since the population is increasing steadily and faster than ever, I was wondering if we could ever reach the turning point.

Given the 'facts' from this source are fully correct, I am left with two questions:

How many years will have to pass for those living to exceed those dead on Earth (assuming we don't populate/colonize another planet).

(This first question is purely asking about the math, excluding the question of the availability of food, housing and other resources).

Is it even remotely possible for the living population to exceed the dead population before we turn extinct or run out of space?

$\begingroup$no turning point without increasing life expectancy - and it will be temporary state. Immortality may help.$\endgroup$
– MolbOrgDec 26 '16 at 18:05

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$\begingroup$This could only happen if breakthroughs in medical tech allow people to live longer then ever, standards of living shoot up and there are far more resources thanks to "fusion, nanotech or buzzword of choice" AND cultural baby boom.$\endgroup$
– Donald HobsonDec 26 '16 at 19:45

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$\begingroup$The population is not increasing faster than ever. The world-wide population growth is down to 1% per year and most projections are that by the end of the century it will be zero or negative. This is actually a serious problem -- nobody has the faintest idea of how to run a world in which the population decreases.$\endgroup$
– AlexPDec 26 '16 at 22:39

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$\begingroup$to get live population larger than dead population you need growth rate greater than 1/life_expectancy, and you need to sustain that growth rate, because if growth rate is less than 1/life_expectancy you're adding dead faster than you're adding living.$\endgroup$
– JasenDec 27 '16 at 1:17

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$\begingroup$Everyone would die of starvation, but if 2.5 billion women could get pregnant and have 4 kids each that is 10 billion kids/yr. So if your could sustain that for about 12-13yr then yes. Otherwise with 1 kid per per year it would be >48yrs and you would have to counter even more deaths.$\endgroup$
– cybernardDec 27 '16 at 3:36

9 Answers
9

Like other answers said, it is not practically possible at this point for Earth to sustain a population greater than number of people already dead. Unless you assume that every woman on the Earth for some strange reason decide to give birth each one:

So in the case that every woman now decide to give birth to 31 children (well in reality should be 40: we have to take into account people that would die in the meanwhile and keep a good error margin), and assuming (each pregnancy last 9 months) that in the middle of the process we will not end the available food (at some points we will have 60 billions people to feed and the Whole process would last 40 years), then yes it is theoretically possible.

However there's no way we could do that in general:

Assume that population keeps constantly doubling: in that case the sum of dead people and living people would be almost the same, but a double growth rate is not sustainable, at some point it will slow.

To keep living population greater than dead population then you need a growth rate that is more than constant doubling ( x3, but also x2.1 is fine... or even x2.00001 and so on), and that is even less sustainable that a doubling growth rate.

While in theory it is possible to exceed that limit for now (assuming enough resources), we will quickly reach a limit that will not allow us to exceed that again.

When number of children a woman can give birth in a life will be lesser than

Sum of dead people / sum of living women

Then we will not be able to exceed that limit again. (well in theory we could do that in a hundred of years, assuming we can keep a exponential grow of population for so long).

$\begingroup$This is the correct answer, and should be the accepted one. The fact that population growth rates are currently decreasing is completely irrelevant.$\endgroup$
– Dawood ibn KareemDec 27 '16 at 10:32

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$\begingroup$I just re-read everything, and I agree @DavidWallace and have changed my accepted answer.$\endgroup$
– RoberrrtDec 28 '16 at 8:52

$\begingroup$Since women are not fertile for 40 years, you'll need to start thinking twins. Or triplets.$\endgroup$
– WhatRoughBeastJan 15 at 14:40

$\begingroup$But regarding the first part of the question, wouldn't it still be possible that, given an unlimited amount of time, the dead population would exceed the living?$\endgroup$
– RoberrrtDec 26 '16 at 17:21

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$\begingroup$@Roberrrt According to your link, there were 46 billion dead people by 1 AD. Since future population is unlikely to ever pass this level, then the dead will always and have always outnumbered the living.$\endgroup$
– kingledionDec 26 '16 at 17:31

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$\begingroup$It's impossible to actually know population growth rates beyond say September of 2017, and that only if you have an accurate count of pregnancies and good statistics on miscarriage &c. Anything else is just guesswork tempered by wishful thinking. Unforseen circumstances could produce an abrupt jump or fall, as your graph shows happened around 1950-1970.$\endgroup$
– jamesqfDec 26 '16 at 20:06

$\begingroup$@jamesqf The abrupt 'jump' was the genocide of ~30 million of Chairman Mao's subjects in the 'Great Leap Forward' of 1958-1961. Considering that this significantly increased the ranks of the dead at the expense of the living, I can say with confidence that 'unforeseen circumstances' are not going to cause an abrupt 'jump' in population increase.$\endgroup$
– kingledionDec 27 '16 at 16:14

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$\begingroup$I wonder how much that Graph includes the fact that we keep on living longer and longer on average. Though we probably never will have more living than dead, I wonder if that might change if we start colonizing the Galexy and reach lifetimes of thousands of years.$\endgroup$
– RyanDec 27 '16 at 17:49

Great question. This is one of the questions that my friends and I have asked at various points in our lives. (also: how long would it take for N monkey, typing randomly, to create Macbeth spontaneously?)

The population data SEEMS wrong. Why? My suspicious arise because there is no mention of estimated lifespans or the rate of death in ancient populations. Let's try to fill in some of these and see where that gets us:

Lifespan: let's estimate 40 years. (By this measure, Jesus was normal by actuarial standards)
Death rate: if the lifespan is 40 years, then for every cohort of 1000 people, there would be 25 deaths per year (1000/40 = 25).

Plug these numbers into a spreadsheet and see that a starting population of 5M in 8000 BC would grow to 5e192 by the year 1 AD. !!! SOMETHINGS WRONG HERE !!!

Looking more closely, at a birth rate of 80 per 1000 per year (and a death rate of 25 per 1000 per year), 5M people would grow to 10M in 13 years. This is much higher than the flat line shown in all of these growth models.

If you assume the rate of birth is steady at 80/1000, you need to jigger the death rate to over 79.48 to achieve the stated population of 300M by 1AD.

I'm thinking that the number of births is too high: one would have to look at the model demographics to see if this is realistic: Assume an evenly-distributed cohort of 1000 persons, with ages ranging from 0 to 40. this places 25 people per age. Assume that the fertile years are from 15-40, etc. and you can really look at a more realistic model of populations. (for example, half of those born would not be able to give birth...)

To sustain a lot of births and keep a slowly growing population, you need to have a lot of deaths. We need numbers like infant death rates and the risk of death during childbirth. If they are huge (79.48 / 1000), this can get you to 300 million by 1 AD on a smooth glide path. Doing so would require 47 billion people to be born in this span--a truly epic slaughter. (this might be the way that the referenced numbers were achieved)

It is possible, though, to look at the rate of birth and death in primitive populations in the Amazon, New Guinea, or Kalahari tribesmen. I suspect that this would suggest birth rates at 50 per 1000 (I'm not asserting this--i'm probably wrong); It's probably not a good idea to gauge ancient birth rates from any data collected anywhere after 1800. Increasing urbanization, medical, food improvements, and access to petroleum-based energy added an artificial stimulus to growth rates that probably did not exist in earlier eras.

With these numbers, it would only require 28 billion people to be born in this time.

My suggestions are: (1) define a model that accounts for realistic birth behavior and more detailed methods of death. See what models suggest from this. (2) try to find some proxy for historical birth rates form archaeology or comparative anthropology.

$\begingroup$Between disease and war, death in childbirth, and other factors, I think the death rates WERE quite high. The average life expectancy of 40 is likely too high. I've heard closer to 25, mostly due to how many infants died before the age of 5.$\endgroup$
– ErikDec 27 '16 at 9:17

$\begingroup$"Death rate: if the lifespan is 40 years, then for every cohort of 1000 people, there would be 25 deaths per year (1000/40 = 25)." - less than half of born lived long enough to be 20 years old(or something like that) - they died on all stages infant, young etc. If one survived up to 20-25+ then he had good chances to live longer (do not remember the source trough, but seems reasonable for other things I know). Watch this, that's funny youtube.com/watch?v=yhP2dT-Nar4$\endgroup$
– MolbOrgDec 27 '16 at 17:34

$\begingroup$Please format your equations. Also no need to show steps for your algebra; we all (reasonably) know how to solve basic equations.$\endgroup$
– user22732Dec 26 '16 at 21:35

$\begingroup$it should look more like $$\int_{2017}^{X} (birth\_rate(t)-death\_rate(t))dt>\int_{begin\_of\_time}^{2017} death\_rate(t)dt=Total\_death(2017)$$ you have different sum of death's and you do no distinguish them and because of that they are equal for you and you probably get wrong results. this have to be solved for X and for set of possible birth rates. Something like that.$\endgroup$
– MolbOrgDec 27 '16 at 17:07

$\begingroup$@MolbOrg I was thinking sum at the yearly level. I did not know this site did tex. Sum of deaths is sum of death. They are not different. X is number for fixed ratio.$\endgroup$
– paparazzoDec 27 '16 at 17:13

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$\begingroup$@DavidWallace If we don't agree on the answer then no purpose to him formatting. I tried putting in a Latex sum and I thought it looked busy.$\endgroup$
– paparazzoDec 27 '16 at 17:50

$\begingroup$@DavidWallace because it wasn't my point, it is just a way to write what I mean and I do not mean it is more accurate then OP's stuff and I'm pretty ok with OP's formatting its clear and relatively simple.$\endgroup$
– MolbOrgDec 27 '16 at 17:53

The only way it can happen is with immortality plus a major jump in the available living space (space colonization in a major way, or else interstellar colonization if we already have major space colonization before immortality is developed.) Your question requires the answer to two unknowns in order to answer and thus there is no way to answer it.

Easy Answer: Zombies! Or some other mass resurrection. The math doesn't support it any other way, as has been pointed out in all of these other fine answers.

Another possibility would be cloning on an enormous scale. The only problem with massive cloning is that it serves no purpose in the stated premise. If we can't leave the planet, Mother Earth will slap down the population growth one way or another. Either her or our own hubris will prevent growth of the living to surpass the dead. Remember that the planet is a closed system.

Here is one way the living and the dead could reach population parity. If we had the means to store consciousness in a computer, and then archive everyone alive today. Then, as people die, the become activated in this new digital Elysium. Grant them rights and agency on par with those still in the "meat space". You would be then, in essence, granting immortality that maybe could work within the closed system of Earth without the great mother earth slap down.

Here we have 2 major points in life cycle, birth and death. Each life meets both points.
More birth = more death (after life lasting cycle).

Conclusion - we can never get equal or even get near to the dead population.

Exception is if tomorrow women start giving birth to babies like pop corn. Lets say we have 7 billion people, and lets divide population this way (for example), 25% children, 25% men, 25% old folks, and 25% women. 25% from 7 billion is 1,750,000,000. To get the number of 107 billion living people, each woman need to breed 57.143 children during this life. Since more people would die till all of this women in labor meet their ends, number is slightly increasing to around 62 babies per woman.

Exception no. 2 is immortality. No need to write much about that.

Conclusion no. 2 - planet Earth is perfect in doing one thing, recycling. Every living being is recycled after death, and who knows how many other forms of life that brings. I'd say that number of living and dead is always the same, the only thing that is changing is people. (judging by the fact that we are all recycled)

It probably already has. According to several books that I've read on lineage all modern humans can be traced back to one group of 500-3000 people who lived about 100,000 yrs. ago, meaning that apparently we've almost gone extinct before for whatever reason. Adding in things like the Black Death epidemic and the fact that it took until 1900 or so for the population of living humans to reach 1 billion, the total number of humans who've ever lived isn't nearly as great as you'd think.

$\begingroup$The page that the question links to an article that cites 108,000,000 humans having lived between 50,000 years ago and the year 2011. Note that an event such as the Black Death, if we did not know about it, would cause us to undercount the number of dead people. Do you have any data relevant to this question, or are you just making guesses about possible errors in a study you've never read?$\endgroup$
– David KDec 26 '16 at 22:51

$\begingroup$No...If u suddenly kill off a bunch of people, u have prevented them for reproducing, which means that have just reduced the population size...Their offspring don't die because they're never born, remember..The bigger the population, more deaths in any given span of time. Killing off a large percent of a population limits the total number of deaths in future generations until population reaches its previous size.$\endgroup$
– HarlemmeDec 26 '16 at 23:47

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$\begingroup$You are looking at this as a problem of projecting into the future, but we are the future to the Black Plague. To estimate how many people have lived we have to project from the present day backwards into the past. An event that killed off a large number of people in the past doesn't affect our knowledge of how many people lived after the event, but it does affect our knowledge of how many lived before.$\endgroup$
– David KDec 26 '16 at 23:53

$\begingroup$I'm speaking in the sense that if the Plague hadn't happened, the number of people who've died since then would be much larger.$\endgroup$
– HarlemmeDec 27 '16 at 0:48

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$\begingroup$If the Plague had not happened, perhaps the number of people alive right now would be greater than it is. But it did occur, people who estimate the dead population know about it, and at least some of them take it into account. The irony of historical population "forecasting" is that the later numbers are known relatively well; it is the earlier numbers that are most uncertain, and the higher you assume the growth rate to be the fewer dead people you will think it took to produce the later generations. Negative growth rates have the opposite effect.$\endgroup$
– David KDec 27 '16 at 3:52